Archive for the ‘Biology’ Category

Hallucinations tend to be associated with psychosis, but the reality is more complicated than that. Some people who hear voices don’t suffer from other mental health problems, and the voices they hear aren’t distressing. These “non-clinical voice-hearers” provide an important opportunity to understand hallucinations without the complications of mental illness or medication.

A preliminary study published this week in the journal Brain reports that non-clinical voice-hearers were more likely to detect language in a recording of distorted speech. Voice-hearers also showed some different patterns in brain activation as they listened. The results could help to explain why some people are more likely to hear voices, as well as help to direct future research on the topic.

Hearing meaning in noise

Ben Alderson-Day, the lead author on the paper, is a psychologist at Durham University whose research focuses on auditory hallucinations. To investigate differences of perception in voice-hearers, Alderson-Day and his colleagues used sine-wave speech, which strips out some of the most vital acoustic properties of speech and leaves something that sounds kind of like a series of clicks and whistles. It’s possible to understand it—once you already know what it says, or once you’ve listened to quite a bit of sine-wave speech. (Listen to some examples here.)

If you’ve ever wondered whether psychotherapy achieves meaningful, long-term change in a person’s life, wonder no more: combined evidence from multiple studies suggest that it does. A meta-analysis published recently in Psychological Bulletin reports that a variety of different therapeutic techniques results in positive changes to personality, especially when it comes to neuroticism, that last over a considerable period of time.

Personality is, as your intuition might tell you, relatively stable—people who start out gregarious and adventurous tend to stay gregarious and adventurous throughout their lives. Assessments of people’s personality traits taken at different times tend to agree pretty well with each other. But that doesn’t mean personality is static: personal growth, life experiences, and age all play their part, and people’s personalities do change somewhat throughout their lives—usually for the better.

An OCEAN of change

But it can be tricky to work out precisely what is being evaluated in measures of personality like the “Big Five” of Openness to experience, Conscientiousness, Extraversion, Agreeableness, and Neuroticism (“OCEAN”). Any personality questionnaire will come up with metrics that capture both someone’s stable, long-term tendencies (their traits), as well as how they are feeling in a given moment or phase in their life (their state). So, it’s not enough to find that therapy brings about personality changes—it’s also necessary to figure out how deep those changes go.

When engineers look at mussels, they’re typically looking in awe at how they anchor themselves to nearly every surface imaginable, all while under water. The fibers they use to attach themselves are incredibly strong, and the adhesive works wet or dry on all sorts of materials. For the most part, engineers are looking to create a substance with similar properties.

This week, however, brings an exception: engineers who want to try to keep mussels from sticking to everything. Zebra mussels, a species that has invaded the Great Lakes, is estimated to cost utilities hundreds of millions of dollars each year due to clogged pipes and intakes. Ships, buoys, and pretty much anything else we put in the water also ends up needing to have mussels cleared off.

The international team behind the new work has designed a material that mussels can’t seem to get a grip on. It’s not because the mussel’s adhesive fail; instead, the mussel itself doesn’t seem to know what it’s touching when it’s set down on the material.

Spider silk has some amazing material properties, so there’s lots of enthusiasm for the prospect of using it to make something useful. Unfortunately, spiders aren’t domesticated, and attempts to make the silk proteins in other organisms haven’t been entirely successful. And then there’s the matter of what to do with silk once you have it. It doesn’t always cooperate with modern manufacturing techniques.

But some researchers in India figured out a way to get spider silk to play nicely with lasers. Under the right conditions, the silk itself helps amplify a laser’s power, to the point where it can either cut the silk in specific locations, or soften it to the point where it can be bent or welded.

The work relies on a physics effect termed “nonlinear multiphoton interactions.” In the simplest terms, the effect allows two photons of a given energy to act as a single photon of twice the energy (higher combinations are also possible). It’s a nonlinear effect, since it involves a sudden jump in energy; you don’t end up with any photons in between, at 1.5x the original energy.

There’s a reason why the premise of American Gods is so alluring: the US is home to a wild and glorious mishmash of gods, folktales, and cultural heritage. One by one, groups from around the world picked up and landed on a new shore, bringing their stories with them.

The mere existence of certain tales can be revealing. They develop and mutate as they get passed from one group to the next, and the best stories are passed on more readily. Understanding the spread of folktales can help us understand cultural evolution more generally, and a paper in this week’s PNAS does just that by combining data on folktales with genetic, geographic, and linguistic information.

Researchers studying cultural evolution use biological evolution as a starting point for their ideas, but they also point out that clear and important differences separate the two types of evolution. The timescales, for instance, are often very different—cultural units can be transmitted between people of the same generation, while powerful ideas (like religions) can spread incredibly quickly and easily. A lot of work in cultural evolution is dedicated to trying to divine the mechanisms that underlie the spread of cultural ideas. How do people choose which ideas to adopt? And how does the spread of ideas compare to the spread of genes?

In the Padang Highlands of western Sumatra, a large island in Indonesia, there is a small cave called Lida Ajer that has long offered up clues about human history. Dutch paleoanthropologist Eugene Dubois first excavated the cave before 1890, and Lida Ajer has turned up plenty of preserved animal remains since, including teeth that were identified as human in 1948.

It’s only now that the cave has been carefully and thoroughly dated, providing a new line of evidence that our species was in the region more than 60,000 years ago. That’s 20,000 years older than the previous oldest skeletal evidence of humans in the area. But these new dates line up with existing genetic evidence, as well as with reconstructions of the climate and sea levels at the time.

In a paper published in Nature this week, Kira Westaway of Macquarie University in Australia and her colleagues report what they found when they revisited the discoveries of Lida Ajer. They re-examined the teeth, pointing to all the evidence that the teeth did indeed belong to anatomically modern humans rather than orangutans or other primates. And they carefully dated the cave site to establish how old the teeth were likely to be.

The latest proposal to up that rigor is a big one: 72 researchers from a range of disciplines have drafted a manuscript arguing that the threshold for claiming “statistical significance” should become much stricter. There’s often a fair amount of consensus on how science could be improved, but this suggestion has stimulated some intense debate.

Statistical significance in a very small nutshell

Statistical significance is a concept underlying a huge amount of science—not just psychology or social sciences, but medicine, life sciences, and physical sciences, too. “Significance” used in this way doesn’t mean the importance or size of a finding, rather it’s the probability of that finding showing up in your data even though your hypothesis turns out to be wrong.

The latest proposal to up that rigor is a big one: 72 researchers from a range of disciplines have drafted a manuscript arguing that the threshold for claiming “statistical significance” should become much stricter. There’s often a fair amount of consensus on how science could be improved, but this suggestion has stimulated some intense debate.

Statistical significance in a very small nutshell

Statistical significance is a concept underlying a huge amount of science—not just psychology or social sciences, but medicine, life sciences, and physical sciences, too. “Significance” used in this way doesn’t mean the importance or size of a finding, rather it’s the probability of that finding showing up in your data even though your hypothesis turns out to be wrong.

Randall Munroe, creator of popular webcomic XKCD, recently published a new book called Thing Explainer: Complicated Stuff in Simple Words, in which he uses only the thousand most common words in the English language to explain how a variety of things work, from locks to nuclear bombs. Monroe’s publisher, Houghton Mifflin Harcourt, also publishes textbooks, and when editors in the textbook division saw proofs of Monroe’s Thing Explainer, they realized that his simple explanations could be used to augment high school textbooks.

You know, the old strategy employed ineffectively by dad joke-tellers everywhere: get the #teens on your side with humor.

(credit: Randall Munroe)

Luckily, Munroe’s Thing Explainer comics are absurd enough in their hyper-simplicity that they have a shot at breaking down the walls of sarcasm and ennui encircling the most eye-rolling of high school students.